Abstract: The conductive material in an RF coil disposed in the polarizing field of an NMR apparatus in miminized and the current density at each point in the coil kept constant by providing an inductive element and a set of tapered, interidigtated capacitors having a uniform gap therebetween. The invention maximizes the current-carrying capacity of the coil.

Abstract: The invention provides highly sensitive NMR probes for spectroscopy and microscopy. Thin-film superconducting coils on planar substrates are inductively coupled to form an RF transmitter/receiver. Two embodiments are illustrated. The first, which is particularly suited to liquid samples, uses two coils are positioned on opposite sides of a sample, with their long axis parallel to the axis of the sample. The coils are sized and positioned to maximize SNR, field homogeneity or field strength. In the second embodiment, circular coils are deposited on a substrate having a central aperture. Several coils in a solenoidal configuration are positioned orthogonal to and surrounding the sample.

Abstract: A resonant coil for nuclear magnetic spectroscopy and microscopy is provided, in which the coil is in the form of nested, interrupted loops of a conductive material forming a distributed inductive element and having a plurality of capacitive elements with capacitance distributed over the periphery of the loops. The coil is preferably formed as a thin film of a superconductive material on an electrically nonconductive substrate.

Abstract: In Nuclear Magnetic Resonance (NMR) spectroscopy and microscopy, noise from the receiver coil of the probe limits sensitivity. This noise may be reduced by cooling the receiver coil. Noise may be even further reduced by use of a superconducting receiver coil. However, high temperature superconductors must be maintained at temperatures significantly below the critical temperature, typically in the range of 10-60 K for proper performance. The invention provides an apparatus for cooling an NMR receiver coil to a desired temperature using a closed circuit refrigeration system. A cold fluid is circulated to a heat exchanger which is in thermal contact with a thermally conductive substrate having low magnetic susceptibility. The receiver coil is deposited on a portion of the substrate located distally from the heat exchanger. In the preferred embodiment, the substrate is sapphire and the receiver coil is a superconductive oxide.

Abstract: An array antenna includes a means of thermally isolating the feed network from the space illuminated by the antenna. Filtering layers are incorporated into the structure between the feed and the radiating patches. These filtering layers are transparent to radiation in the frequency range of operation of the antenna, primarily microwaves and millimeter waves, but reflect much shorter wavelengths such as infrared and visible light. This rejection of short wavelengths results in reduced heating of the feed network and so to a reduced heat load on a cooling system. One preferred embodiment employs the radiation shield to advantage by incorporating superconductive elements in the antenna. These elements can be cooled efficiently enough to be practical due to the rejection of heat by the incorporated filtering layers.

Abstract: A method for producing multilayer structures comprised of materials with incompatible processing parameters is disclosed. A bonding layer of arbitrary dielectric constant is applied to each of two substructures. Each substructure is composed of a substrate and at least one epitaxial crystalline layer. Examples of particular bonding materials used are polyimide, fluorocarbon polymers, other organic materials, and glass. The bonding material may be applied like photoresist, or sputtered, or applied in any appropriate manner consistent with the processing constraints of the crystalline materials. Structures formable in this way include superconductor-amorphous dielectric-superconductor and ferroelectric-insulator-semiconductor trilayers, as well as microwave resonators and multichip modules.

Abstract: A novel method of producing weak-link grain boundary Josephson junctions in high temperature superconducting thin films is disclosed. These junctions are reliably and reproducibly formed on uniform planar substrates (10) by the action of a seed layer (40) placed intermediate the substrate (10) and the superconductor film (20). The superconductor film (22) grown atop the seed (42) is misoriented from the rest of the film (24) by an angle between 5.degree. and 90.degree.. The grain boundary (30) so formed acts as a high quality weak-link junction for superconductor devices. The performance of these junctions can be improved by the addition of buffer layers (50, 60) between the substrate (10) and the superconductor film (20).

Abstract: A broadband matching network for coupling a magnetic resonance probe to a preamplifier utilizes superconducting matching coils and superconducting locatable shields to detect very weak magnetic signals over a broad bandwidth. The superconducting matching coils and shields minimize signal loss in the matching amplifier. When used with a superconducting magnetic resonance probe, the circuit provides a significant broadening in bandwidth over that of the probe without loss of performance.